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Engineering is all about improvement, and so it is a science of comparatives. “New, improved” products are ubiquitous, advertised as making teeth whiter, wash fluffier, and meals faster. Larger engineered systems are also promoted for their comparative edge: the taller building with more affordable office space, the longer bridge with a lighter-weight roadway, the slimmer laptop with greater battery life. If everything is a new, improved version of older technology, why do so many products fail, proposals languish, and systems crash?

To reengineer anything—be it a straight pin, a procurement system, or a Las Vegas resort—we first must understand failure. Successes give us confidence that we are doing something right, but they do not necessarily tell us what or why. Failures, on the other hand, provide incontrovertible proof that we have done something wrong. That is invaluable information.

Reengineering anything is fraught with risk. Take paper clips. Hundreds of styles were introduced in the past century, each claiming to be an improvement over the classic Gem. Yet none displaced it. The Gem maintains its privileged position because, though far from perfect, it strikes an agreeable balance between form and function. Each challenger may improve on one aspect of the Gem but at the expense of another. Thus, a clip that is easier to attach to a pile of papers is also more likely to fall off. Designers often focus so thoroughly on the advantages that they fail to appreciate (or else ignore) the disadvantages of their new design.

Imagine how much more complex is the challenge of reengineering a jumbo jet. The overall external form is more or less dictated by aerodynamics. That form, in turn, constrains the configuration of the interior space, which must accommodate articulated human passengers as well as boxy luggage and freight. As much as shipping clerks might like fuselages with square corners, they must live with whale bellies. It is no wonder that Boeing invited stakeholders, including willing frequent flyers, to participate in designing its Dreamliner—so the users would buy into the inevitable compromises. The resulting jetliner will succeed or fail depending on how convincingly those compromises are rationalized.

Logically speaking, basing a reengineering project—whether of a product or a business process—on successful models should give designers an advantage: They can pick and choose the best features of effective existing designs. Unfortunately, what makes things work is often hard to express and harder to extract from the design as a whole. Things work because they work in a particular configuration, at a particular scale, and in a particular culture. Trying to reverse engineer and cannibalize a successful system sacrifices the synergy of success. Thus John Roebling, master of the suspension bridge form, looked for inspiration not to successful examples of the state of the art but to historical failures. From those he distilled the features and forces that are the enemies of bridges and designed his own to avoid those features and resist those forces. Such failure-based thinking gave us the Brooklyn Bridge, with its signature diagonal cables, which Roebling included to steady the structure in winds he knew from past example could be its undoing.

But when some bridge builders in the 1930s followed effective models, including Roebling’s, they ended up with the Tacoma Narrows Bridge, the third-longest suspension bridge in the world and the largest ever to collapse in the wind. In the process of “improving” on Roebling’s design, the very cables that he included to obviate failure were left out in the interests of economy and aesthetics.

When a complex system succeeds, that success masks its proximity to failure. Imagine that the Titanic had not struck the iceberg on her maiden voyage. The example of that “unsinkable” ship would have emboldened success-based shipbuilders to model larger and larger ocean liners after her. Eventually the Titanic or one of those derivative vessels would probably have encountered an iceberg—with obvious consequences. Thus, the failure of the Titanic contributed much more to the design of safe ocean liners than would have her success. That is the paradox of engineering—and of reengineering.

Henry Petroski is the Aleksandar S. Vesic Professor of Civil Engineering and a professor of history at Duke University in Durham, North Carolina. His most recent book is Pushing the Limits: New Adventures in Engineering (Knopf, 2004).

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